Contact type two-phase rotary encoders are generally used as an input change-over switch for adjustment of sound volume, tuning and the like in video and audio equipment.
Conventional two-phase rotary encoders generally comprise a ring-shaped common electrode pattern, and two ring-shaped comb electrode patterns formed from an inside to an outside of a concentric circle, with respect to a center hole, for supporting a shaft on a surface of a substrate made of an insulating resin. Two sliders having contacts for electrically connecting the common electrode pattern and the two comb electrode patterns are further provided. An intermittent opening/closing operation is performed by sliding of the contacts on the comb electrode patterns via clockwise/counterclockwise rotation of the two sliders provided on a bottom surface of a rotor mounted to the rotative shaft attached vertically to the substrate.
As illustrated in FIG. 13, in a pulse output equalizing circuit of a Vcc power source of the two-phase rotary encoder 60, pulse signals VA, VB with duty of 50% with different phases are output between a common external connecting terminal C (grounding electric potential) and two external connecting terminals A, B, respectively.
Conventional rotary encoders are disclosed in, for example, Japanese Utility Model Application Publication No. 59-22667, Japanese Patent Application Laid-Open No. 1-258328, Japanese Utility Model Application Laid-Open No. 3-26021, Japanese Patent Application Laid-Open No. 6-94476, Japanese Patent Application Laid-Open No. 7-141960, and Japanese Patent Application Laid-Open No. 7-147116. Such rotary encoders provide various devised electrode patterns of a substrate and contact structures.
Generally, rotary encoders are provided with a click mechanism, so that a rotating operation of the shaft is controlled, and, simultaneously, a rotating angle of the shaft is generally regulated to be integral multiples of the rotating angle corresponding to one click of the click mechanism.
Miniaturization, lower cost and higher reliability of contact type rotary encoders are greatly demanded by the electronic equipment manufacturing market. Since the above-mentioned prior rotary encoders, in which the two ring-shaped comb electrode patterns and the ring-shaped common electrode pattern are concentrically formed on the substrate, need a wide substrate area, however, miniaturization is difficult.
In an attempt to overcome this problem, means for dividing the comb electrode pattern into an arc shape are disclosed in several of the above publications in order to miniaturize the device, but these patterns are complicated, which negatively affects the phase accuracy of two-phase pulse output. Further, adoption of insert molding techniques increases cost and decreases reliability due to displacement problems.
With regards to substrate manufacturing problems, a raised ridge pattern exists on the comb uneven portion of the comb electrode pattern on the substrate in conventional rotary encoders, generating noise due to scraping of the sliders sliding on the comb patterns and the contacts, and abrasion of the patterns due to such scraping negatively influences the reliability thereof. Japanese Patent Application Laid-Open No. 6-94476 discloses means for coating the entire surface of the comb electrode pattern with a resistor material such that the surface becomes flat, and generating a pulse signal by means of a difference in thickness of the resistor on the uneven pattern of the comb pattern. This, however, is more costly, and reliability of properties of the comb electrode pattern is decreased due to a fluctuation of a potential difference of the pulse signal caused by abrasion of the resistor.
There is a demand for a rotary encoder, having a tact switch, which is switched on by pushing the shaft to a shaft direction. However, it is difficult to miniaturize a combination of the rotary encoder mechanism and the tact switch mechanism, and is too costly at this time.